Integrated circuit test power supply

- Megatest Corporation

A power supply for testing an integrated circuit includes a source voltage input terminal for receiving an input voltage. The power supply serves as both a DUT active power supply and an IDDQ measurement circuit, without the need for switching between separate DUT active power supply and IDDQ measurement circuits. In one embodiment, a current source output driver includes a diode across a current sensing resistor inside a feedback loop. This minimizes VDD changes when the DUT demands transient current, such as when loading IDDQ test vectors. Moreover, with decreased transient changes in VDD, dielectric absorption effects of a decoupling capacitor are reduced.

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Claims

1. A power supply for testing an integrated circuit, comprising:

a source voltage input terminal;
an operational amplifier coupled to said input terminal and configured to produce current in response to a feedback signal;
a shunt resistor coupled to said operational amplifier;
a diode coupled in parallel with said shunt resistor;
a current sensor coupled in series with said shunt resistor; and
an output terminal coupled to said resistor, diode and current sensor, said output terminal configured to connect to a device under test.

2. The power supply of claim 1, further comprising a second operational amplifier positioned between said first operational amplifier and said shunt resistor.

3. The power supply of claim 1, further comprising one end of a decoupling capacitor coupled to said diode between said diode and a device under test, and an other end of said decoupling capacitor coupled to a reference voltage, which may be ground.

4. The power supply of claim 1, further comprising an analog to digital converter coupled to said current sensor and configured to generate a digital signal representative of an analog input signal.

5. A precision measurement power supply, comprising:

a source voltage input terminal;
an operational amplifier coupled to said input terminal and configured to produce current in response to a feedback signal;
a shunt resistor coupled to said operational amplifier;
a diode coupled in parallel with said shunt resistor;
a current sensor coupled in series with said shunt resistor; and
an output terminal coupled to said resistor, diode and current sensor, said output terminal configured to connect to a device under test.

6. The power supply of claim 5, further comprising a second operational amplifier positioned between said first operational amplifier and said shunt resistor.

7. The power supply of claim 5, further comprising one end of a decoupling capacitor coupled to said diode between said diode and a device under test, and an other end of said decoupling capacitor coupled to a reference voltage, which may be ground.

8. The power supply of claim 5, further comprising an analog to digital converter coupled to said current sensor and configured to generate a digital signal representative of an analog input signal.

Referenced Cited
U.S. Patent Documents
3617881 November 1971 McCormick
5059889 October 22, 1991 Heaton
5481551 January 2, 1996 Nakano et al.
5514976 May 7, 1996 Ohmura
Patent History
Patent number: 5773990
Type: Grant
Filed: Sep 29, 1995
Date of Patent: Jun 30, 1998
Assignee: Megatest Corporation (San Jose, CA)
Inventors: Jan B. Wilstrup (Mounds View, MN), Stanley Peter Mros (Roseville, MN)
Primary Examiner: Vinh P. Nguyen
Law Firm: Flehr Hohbach Test Albritton & Herbert LLP
Application Number: 8/536,206
Classifications
Current U.S. Class: 324/765; 324/763
International Classification: G01R 1512;